Chemical induction of Budbreak: new generation products to replace hydrogen Cyanamide

The area in apple production in Brazil exceeds 38,000 ha, with 'Gala' and 'Fuji' clones representing 90 percent of total production. Most of the region does not accumulate enough chilling to overcome dormancy on these two cultivars. Chemical induction of budbreak has been widely used in commercial apple production in Brazil since the 1970’s. Earlier products include mineral oil combined with dinitro ortho cresol (DNOC) and ortho dinitro butyl phenol (DNOBP). Registration of the salts of dinitro was cancelled in the 1980's. Since that time growers have used the mix of mineral oil and hydrogen cyanamide (HC). Due to the potential prohibition of HC in some European countries, we have conducted experiments to identify products with action in the induction of budbreak on apple trees. Our aim has been to find a replacement for HC that is less toxic. The main desirable characteristics for a HC replacement is that it must be low cost, efficiently induce sprouting and exhibit minimal toxicity for plants and the environment. Despite the large number of substances effective in inducing sprouting, few are accepted and used commercially, and the high cost and toxicity of these compounds are the main factors limiting their commercial potential. Among the products tested as replacements for HC were Erger®, Syncron® and Vorax®, all in admixture with calcium nitrate or mineral oil. Formulations of mineral oil and mineral oil admixed with adhesive spreader-type silicon have also been evaluated. Erger®, Syncron® and Vorax® mixed with calcium nitrate or mineral oil exhibited effects on axillary and terminal budbreak similar to the standard treatment of mineral oil and HC. Our results demonstrate that Erger®, Syncron® and Vorax® were effective in inducing bud break and flowering in apple trees and can efficiently replace HC.